U.S. Commissioner of the International Boundary and Water Commission Edward Drusina, right, seated, announces the expansion of a far-reaching water conservation agreement that governs how the U.S. and Mexico manage the overused Colorado River, at a news conference in Santa Fe, N.M., on Wednesday, Sept. 27, 2017. (AP Photo/Morgan Lee)

SANTA FE, N.M. (AP) — The United States and Mexico unveiled an agreement Wednesday to preserve the overtaxed Colorado River, including spending millions of dollars on conservation and environmental projects and drawing up plans to deal with any shortages amid drought and climate change.

The United States pledged to invest $31.5 million in water conservation projects in Mexico, such as lining irrigation ditches with concrete to reduce leaks and upgrading irrigation equipment to use less water.

The water saved would be divided among the two nations and environmental projects.

In addition to the conservation savings, the agreement sets aside another 210,000 acre-feet (260 million cubic meters) of water for environmental projects. One acre-foot (1,200 cubic meters) is enough to supply a typical U.S. family for a year.

The two nations and a coalition of charitable foundations also agreed to contribute a total of $18 million for environmental restoration, research and monitoring.

The nine-year agreement is an amendment to a 1944 treaty that governs how the U.S. and Mexico share and manage the river, which flows through both nations. It expands on a 2012 amendment that expires at the end of this year.

Details of the new amendment were released at a water conference in Santa Fe, New Mexico.

The Colorado River is vital to the southwestern U.S. and northwestern Mexico. It supplies water to about 40 million people and 6,300 square miles (16,300 square kilometers) of farmland in the U.S. alone. Equivalent figures for Mexico weren’t immediately available.

The river begins in the Colorado mountains and winds 1,400 miles (2,250 kilometers) to the Mexican states of Sonora and Baja California.

The agreement is a commitment to future generations to solve the river’s problems “so that they don’t say that our generation stood there with our arms crossed,” said Roberto Salmon, Mexico’s representative on the International Boundary and Water Commission, a U.S.-Mexican organization that oversees the two nations’ boundary and water treaties.

Salmon spoke in Spanish.

Edward Drusina, the U.S. representative, said the agreement provides more certainty to water managers struggling to deal with changing conditions.

“It is not necessarily the complete fix to the system because we don’t know what lies around the corner,” he said.

The agreement allows Mexico to store some of its share of the river water in Lake Mead in the United States if it cannot use it immediately. Mexico can withdraw it later, subject to some conditions.

That’s important because Mexico has few reservoirs in the northwest part of the country, said Osvel Hinojosa of the Mexican conservation group Pronatura Noroeste.

“The idea is to conserve and store and try and avoid a shortage,” Hinojosa said, speaking in Spanish.

The charitable foundations “are eager to do their share to make sure the agreement is implemented and successful,” said Ted Kowalski, director of the Walton Family Foundation’s Colorado River Initiative and one of the groups involved.

The others include the S.D. Bechtel Jr. Foundation, the William and Flora Hewlett Foundation, the Gordon and Betty Moore Foundation, the International Community Foundation and the Water Foundation.

Other provisions of the agreement:

— Both countries will draw up contingency plans to deal with any shortages of water in the river amid drought and climate change.

— Both countries agreed to share the burden of any shortages and the benefits of any surpluses in the Colorado River.

— The International Boundary and Water Commission will study ways to reduce salt levels in the Colorado River that reaches Mexico. The water picks up salt from the soil when it is used for irrigation and returned to the river; too much salt makes it unusable for agriculture and drinking.